The present application is directed to improving the selection of printer colors. More particularly, the present application is directed to an enhancement of image gamut and will be described with the particular reference thereto. However, it is to be appreciated that the present application is applicable to other like applications.
In order to render an image on an output color device, the image colors have to be mapped to the color gamut of the output device. Gamut mapping serves to map pixels defined by colors not printable by the printer or resulting from initial image processing, into colors printable by a real printer. In doing so, out-of-gamut, unprintable colors are mapped to printable colors in accordance with some scheme designed to maintain color intent and aesthetic appearance. Traditionally, the gamut mapping has been used to reduce the color gamut of the image, e.g. complete set of colors found within an image at a given time.
In recent years, however, the gamut of the rendering devices has been substantially improved so that any given image may only use a small fraction or range of the available device colors. In this context, digitizing a photograph, converting a digitized image to a different color space, or outputting the image to a given medium using a certain output device generally alters the image gamut in the sense that some of the colors in the original image are lost in the mapping process while a large portion of the device gamut remains unused.
It would often be desirable to expand the image gamut to better utilize the printer gamut. One approach to expand the image gamut is to non-linearly distort or warp the image colors. However, such an approach is computationally complex and costly.
Another approach to expand the image gamut is to apply a generic expansion to the image gamut, e.g. increase chroma values of all pixels in the image. Because such generic chroma expansion generally leads to some color values being outside of the device gamut, one of the gamut mapping methods, such as clipping, is typically applied to bring the expanded colors within the device gamut. However, such gamut clipping is undesirable as it might destroy the spatial detail and produce objectionable artifacts in the resultant image.
There is a need for methods and apparatuses that overcome the aforementioned problems and others.